ANDROID: GKI: Enable CONFIG_USB_DWC3

Many platforms are using this so just build it in to make it simpler for
testing and for a smaller exported API.

Bug: 157965270
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ia5c92e22f61066411abfa766f3ce109fa86a915b